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R L Weiss

Publications and source records attributed to R L Weiss.

At least 19 recordsLinked to original sources
PubMed1992

Arginine transport in mitochondria of Neurospora crassa.

Transport of arginine into mitochondria of Neurospora crassa has been studied. Arginine transport was found to be saturable (Km = 6.5 mM) and to have a pH optimum of pH 7.5. Mitochondrial arginine transport appeared to be facilitated transport rather than active transport because: (i) the arginine concentration within the mitochondrial matrix after transport was similar to that of the reaction medium, and (ii) uncouplers and substrates of oxidative phosphorylation did not affect the transport rate. The basic amino acids ornithine, lysine, and D-arginine inhibited arginine transport. The arginine transport system could be irreversibly blocked by treating mitochondria with the reactive arginine derivative, N-nitrobenzyloxycarbonyl-arginyl diazomethane.

Amino Acids↗
PubMed1992

Ornithine decarboxylase activity in tumor and normal tissue of head and neck cancer patients.

Tumorigenesis requires increased biosynthesis of polyamines and elevated levels of ornithine decarboxylase, which is the rate-limiting enzyme in the polyamine synthesis pathway. Previous animal studies have noted a marked increase in ornithine decarboxylase after exposure to tumorigenic stimuli and that pretreatment with vitamins A and E provides protection against the carcinogenic action. However, studies of ornithine decarboxylase activity in human oral cavity carcinoma have not been as specific. The goal of this study was to determine whether a specific difference in ornithine decarboxylase activity occurs in tumor versus adjacent normal tissue in head and neck squamous cell carcinoma patients. Ornithine decarboxylase activity was measured in 30 consecutive head and neck cancer patients undergoing surgical therapy. Ornithine decarboxylase levels were found to be significantly elevated in tumor tissue samples when compared to adjacent normal mucosa samples (P less than .004). This finding confirms the previous findings noted in animal models and implies that the protective effects of vitamins A and E will extend to human head and neck cancers.

Carcinoma, Squamous Cell↗
PubMed1992

A clinical laboratory management elective for pathology residents.

Many practicing pathologists, particularly those in private settings, function as managers. Their responsibilities may not only involve directing the successful activities of laboratory personnel, but often require a level of accountability to hospital administrators or business managers. Traditional training programs focus on technical competency and devote little time, if any, to preparing their graduates for the management aspects of their careers. In response to this need, a 1-month elective was designed for senior pathology residents at the University of Utah, Salt Lake City. The cumulative experiences of a large academic pathology department and its successful commercial laboratory venture provided a real-world supplement to a curriculum founded in basic business management principles.

Curriculum↗
PubMed1991

Diagnosis of cytomegalovirus pneumonitis on bronchoalveolar lavage fluid: comparison of cytology, immunofluorescence, and in situ hybridization with viral isolation.

Forty-three bronchoalveolar lavage (BAL) specimens from 40 immunocompromised patients were studied for the presence of cytomegalovirus (CMV) by rapid diagnostic methods. DNA in situ hybridization, cytology, and immunofluorescence were compared to conventional cell culture. Eleven (25%) of the 43 BAL samples grew CMV in culture. In situ hybridization detected 6 of these 11 for sensitivity, specificity, and predictive values of positive and negative of 55%, 94%, 75%, and 86%, respectively. Cytology had a sensitivity of 73% and specificity of 100%. Six Papanicolaou-stained cytospins were screened cytologically versus one hybridization cytospin, and the higher sensitivity of cytology may reflect this extensive sampling. The immunofluorescent method had a sensitivity equal to that of cytology (73%): however, the specificity (72%) was significantly less than that of either the probe or cytology. These data suggest that although in situ hybridization can be a rapid, useful method for detecting CMV in BAL specimens, cytology appears to be a more sensitive method.

Bronchoalveolar Lavage Fluid↗
PubMed1990

Efficiency factors and ATP/ADP ratios in nitrogen-fixing Bacillus polymyxa and Bacillus azotofixans.

The efficiency factor, the number of moles of ATP generated per mole of glucose fermented, was determined in anaerobic, non-carbon-limited N2-fixing cultures of Bacillus polymyxa, Bacillus macerans, Bacillus azotofixans, and Clostridium butyricum through identification and quantitation of the fermentation products by 13C nuclear magnetic resonance spectroscopy and measurement of acetate kinase activities. All three Bacillus species had acetate kinase activities and produced acetate and ethanol as the major fermentation products. The maximum amounts of ATP generated per mole of glucose fermented were 2.70, 2.64, and 2.88 mol in B. polymyxa, B. macerans, and B. azotofixans, respectively, compared with 3.25 mol in C. butyricum. Thus, in the N2-fixing Bacillus species, the efficiency factors are lower than that in C. butyricum. Steady-state ATP/ADP concentration ratios were measured in non-carbon-limited N2-fixing cultures of B. polymyxa and B. azotofixans through separation and quantitation of the adenylates in cell extracts by ion-pair reversed-phase high-performance liquid chromatography. The observed ATP/ADP ratios were 4.5 and 3.8, and estimated energy charges were 0.81 to 0.86 and 0.81 to 0.83, respectively, for B. polymyxa and B. azotofixans. The results suggest that under these growth conditions, the rate of ATP regeneration is adequate to meet the energy requirement for N2 fixation in the Bacillus species, in contrast to N2-fixing Clostridium pasteurianum and Klebsiella pneumoniae, for which substantially lower steady-state ATP/ADP ratios and energy charges have been reported. Implications of the results are discussed in relation to possible differences between Bacillus and Clostridium species in energy requirements for N2 fixation and concomitant ammonia assimilation.

Acetate Kinase↗
PubMed1990

Multilobated B-cell lymphoma. A clinicopathologic study of 24 cases.

The clinical, histologic, and immunologic features of 24 cases of multilobated B-cell lymphoma are presented and compared with those of previously reported cases. Cases were included in this study when more than 50% of the tumor cells had nuclear multilobation. There were 13 males and 11 females with an age range of 13 to 79 years. A slight predominance of node-based presentations was observed. Seventeen patients (71%) presented with advanced (stage III or IV) disease. Complete remissions were achieved in 13 (59%) of 22 patients, and 14 (58%) of the 24 patients were still alive after a follow-up period ranging from 10 to 124 months. The 1-year survival was 65% (SE = 10%). Relapses occurred in 4 (31%) of 13 patients with complete responses. These observations, together with those previously reported, support the conclusion that the multilobated B-cell variant of non-Hodgkin's lymphoma behaves in a fashion similar to that of the intermediate-grade, diffuse, large-cell non-Hodgkin's lymphomas.

Adolescent↗
PubMed1989

Identification of an arginine carrier in the vacuolar membrane of Neurospora crassa.

A number of arginine derivatives were tested for their ability to inhibit arginine uptake into vacuolar membrane vesicles of Neurospora crassa. The guanido side chain and L-configuration were found to be important for recognition by the arginine carrier. Based upon the specificity of recognition, a reactive arginine derivative (N alpha-p-nitrobenzyloxycarbonyl arginyl diazomethane) was synthesized which has an intact guanido side chain and a diazo group at the carboxyl end. The latter decomposes to a reactive carbene group. This derivative inhibited arginine uptake into vacuolar membrane vesicles at low concentrations. Radioactive N alpha-p-nitrobenzyloxycarbonyl arginyl diazomethane was covalently bound to vacuoles. Binding was specific for a single membrane protein with an approximate molecular weight of 40,000, saturable (2 pmol/mg vacuolar membrane protein), and inhibited by 100 mM L-arginine but not by 100 mM L-lysine. The results suggest that this protein is the arginine carrier.

Affinity Labels↗
PubMed1989

Ammonia assimilation pathways in nitrogen-fixing Clostridium kluyverii and Clostridium butyricum.

Pathways of ammonia assimilation into glutamic acid were investigated in ammonia-grown and N2-fixing Clostridium kluyverii and Clostridium butyricum by measuring the specific activities of glutamate dehydrogenase, glutamine synthetase, and glutamate synthase. C. kluyverii had NADPH-glutamate dehydrogenase with a Km of 12.0 mM for NH4+. The glutamate dehydrogenase pathway played an important role in ammonia assimilation in ammonia-grown cells but was found to play a minor role relative to that of the glutamine synthetase/NADPH-glutamate synthase pathway in nitrogen-fixing cells when the intracellular NH4+ concentration and the low affinity of the enzyme for NH4+ were taken into account. In C. butyricum grown on glucose-salt medium with ammonia or N2 as the nitrogen source, glutamate dehydrogenase activity was undetectable, and the glutamine synthetase/NADH-glutamate synthase pathway was the predominant pathway of ammonia assimilation. Under these growth conditions, C. butyricum also lacked the activity of glucose-6-phosphate dehydrogenase, which catalyzes the regeneration of NADPH from NADP+. However, high activities of glucose-6-phosphate dehydrogenase as well as of NADPH-glutamate dehydrogenase with a Km of 2.8 mM for NH4+ were present in C. butyricum after growth on complex nitrogen and carbon sources. The ammonia-assimilating pathway of N2-fixing C. butyricum, which differs from that of the previously studied Bacillus polymyxa and Bacillus macerans, is discussed in relation to possible effects of the availability of ATP and of NADPH on ammonia-assimilating pathways.

Ammonia↗
PubMed1988

Glutamate biosynthesis in Bacillus azotofixans. 15N NMR and enzymatic studies.

Pathways of ammonia assimilation into glutamic acid in Bacillus azotofixans, a recently characterized nitrogen-fixing species of Bacillus, were investigated through observation by NMR spectroscopy of in vivo incorporation of 15N into glutamine and glutamic acid in the absence and presence of inhibitors of ammonia-assimilating enzymes, in combination with measurements of the specific activities of glutamate dehydrogenase, glutamine synthetase, glutamate synthase, and alanine dehydrogenase. In ammonia-grown cells, both the glutamine synthetase/glutamate synthase and the glutamate dehydrogenase pathways contribute to the assimilation of ammonia into glutamic acid. In nitrate-grown and nitrogen-fixing cells, the glutamine synthetase/glutamate synthase pathway was found to be predominant. NADPH-dependent glutamate dehydrogenase activity was detectable at low levels only in ammonia-grown and glutamate-grown cells. Thus, B. azotofixans differs from Bacillus polymyxa and Bacillus macerans, but resembles other N2-fixing prokaryotes studied previously, as to the pathway of ammonia assimilation during ammonia limitation. Implications of the results for an emerging pattern of ammonia assimilation by alternative pathways among nitrogen-fixing prokaryotes are discussed, as well as the utility of 15N NMR for measuring in vivo glutamate synthase activity in the cell.

Ammonia↗
PubMed1987

Ammonia assimilation in Bacillus polymyxa. 15N NMR and enzymatic studies.

Pathways of ammonia assimilation into glutamic acid and alanine in Bacillus polymyxa were investigated by 15N NMR spectroscopy in combination with measurements of the specific activities of glutamate dehydrogenase, glutamine synthetase, glutamate synthetase, alanine dehydrogenase, and glutamic-alanine transaminase. Ammonia was found to be assimilated into glutamic acid predominantly by NADPH-dependent glutamate dehydrogenase with a Km of 2.9 mM for NH4+ not only in ammonia-grown cells but also in nitrate-grown and nitrogen-fixing cells in which the intracellular NH4+ concentrations were 11.2, 1.04, and 1.5 mM, respectively. In ammonia-grown cells, the specific activity of alanine dehydrogenase was higher than that of glutamic-alanine transaminase, but the glutamate dehydrogenase/glutamic-alanine transaminase pathway was found to be the major pathway of 15NH4+ assimilation into [15N]alanine. The in vitro specific activities of glutamate dehydrogenase and glutamine synthetase, which represent the rates of synthesis of glutamic acid and glutamine, respectively, in the presence of enzyme-saturating concentrations of substrates and coenzymes are compared with the in vivo rates of biosynthesis of [15N]glutamic acid and [alpha,gamma-15N]glutamine observed by NMR, and implications of the results for factors limiting the rates of their biosynthesis in ammonia- and nitrate-grown cells are discussed.

Alanine↗
PubMed1987

Purification and characterization of arginase from Neurospora crassa.

We have purified an enzymatically active form of arginase from a wild-type strain of Neurospora crassa to homogeneity. The enzyme has a subunit molecular weight of 38,300 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The native protein migrated as a hexamer during gel-filtration chromatography with an apparent molecular weight of 266,000. The enzyme exhibited hyperbolic kinetics at pH 9.5 with an apparent Km for arginine of 131 mM. Antiserum was prepared against the purified enzyme and used to demonstrate the existence of three cross-reactive proteins in crude extracts of wild-type N. crassa. One of these proteins corresponded to the purified protein, whereas the other two were of molecular weights 41,700 and 26,800, respectively. Using the same antiserum, we found that rat liver, but not rat kidney, contains immunoreactive material. We also detected two proteins in extracts of Saccharomyces cerevisiae that were weakly cross-reactive with the antiserum. These data provide evidence for the existence of multiple forms of arginase in fungi as well as in mammals.

Animals↗
PubMed1987

A single precursor protein for two separable mitochondrial enzymes in Neurospora crassa.

The arg-6 locus of Neurospora crassa encodes two early enzymes of the arginine biosynthetic pathway, acetylglutamate kinase and acetylglutamyl-phosphate reductase. Previous genetic and biochemical analyses of this locus and its products showed that: 1) strains carrying polar nonsense mutations in the acetylglutamate kinase gene lacked both enzyme activities (Davis, R.H., and Weiss, R.L. (1983) Mol. Gen. Genet. 192, 46-50), and 2) the proteins isolated from mitochondria were completely separable (Wandinger-Ness, A., Wolf, E.C., Weiss, R.L., and Davis, R.H. (1985) J. Biol. Chem. 260,5974-5978). These data suggested that the two enzymes were initially synthesized as a single precursor which was subsequently cleaved into two distinct polypeptides. We report here the identification of a high molecular weight protein, synthesized in vitro from isolated N. crassa RNA, that contains sequences corresponding to acetylglutamate kinase as well as acetylglutamyl-phosphate reductase. An analogous precursor was identified in vivo by pulse-labeling experiments. The precursor was similar to other mitochondrial precursors in that its uptake and processing in vivo was rapid and required an intact mitochondrial electrochemical gradient. This represents the first report of a bifunctional protein precursor which gives rise to two mitochondrial enzymes.

Aldehyde Oxidoreductases↗
PubMed1987

Carboxyl-terminal sequences influence the import of mitochondrial protein precursors in vivo.

The large subunit of carbamoyl phosphate synthase A [carbon-dioxide: L-glutamine amido-ligase (ADP-forming, carbamate-phosphorylating), EC 6.3.5.5] from Neurospora crassa is encoded by a nuclear gene but is localized in the mitochondrial matrix. We have utilized N. crassa strains that produce both normal and carboxyl-terminal-truncated forms of carbamoyl phosphate synthase A to ask whether the carboxyl terminus affects import of the carbamoyl phosphate synthase A precursor. We found that carboxyl-terminal-truncated precursors were directed to mitochondria but that they were imported less efficiently than full-length proteins that were synthesized in the same cytoplasm. Our results suggest that effective import of proteins into mitochondria requires appropriate combinations of targeting sequences and three-dimensional structure.

Amino Acid Sequence↗
PubMed1987

Current concepts in the surgical pathology of pulmonary infections.

Among patients with pulmonary infections, those who are immunosuppressed and have pulmonary infiltrates continue to be the most numerous coming to biopsy and present the greatest diagnostic challenge to the surgical pathologist. These are the cases in which immunodiagnostic methods and DNA probes are immediately beneficial. Enthusiasm for application of these new methods for the recognition of infectious agents must be tempered by careful clinicopathologic correlation, since more sensitive methods are likely to pick up more bystander organisms and polymicrobial processes. Nevertheless, the development of organism-specific visualization reagents remains one of the most exciting areas in pathology.

Antibodies, Monoclonal↗